'The Delta breeze saves you'

For the fourth year in a row, Stockton appears to have escaped the summer season with relatively few 100-degree days.

Alex Breitler

For the fourth year in a row, Stockton appears to have escaped the summer season with relatively few 100-degree days.

To what do we owe the pleasure?

"You guys should build a statue in honor of the Delta breeze and put it in your town square," said Bill Patzert, an oceanographer at the NASA Jet Propulsion Laboratory in Pasadena.

Here's his theory:

Over extended periods of time, the Pacific Ocean switches back and forth between generally warmer and generally cooler currents - a phenomenon known to scientists as the Pacific Decadal Oscillation.

Since 2008, the ocean currents have tended to be cooler.

What does that have to do with the Delta breeze? Cooler ocean currents mean cooler air temperatures at the coast, even while the Central Valley cooks.

The larger the contrast between the cool coast and the warmer Valley, the more likely the Delta breeze will kick in each afternoon just as the Valley approaches peak temperatures.

Sure, it's still hot, but that hint of a breeze helps us avoid extreme heat - and, of course, provides immense relief after dark.

"The Delta breeze saves you," Patzert said.

Globally, rising temperatures have leveled off the past six or seven years, he said, but he attributes that to the cooler ocean currents. Longer-term climate change is still a real threat, and we can expect temperatures to begin rising again once ocean currents warm up, he said.

Stockton saw 11 triple-digit days this year. Normal is 18. We haven't had a normal or above-normal year since 2009, when the city topped 100 degrees 21 times.

The city experienced only one significant heat wave this year - seven straight days at or above 100 degrees in late June and early July. Normally we'd have two or three heat waves in one summer, National Weather Service forecaster Johnnie Powell said.

This won't last forever, he said.

"We're still only looking at a short sample in a short area of time," Powell said. Records at Stockton Metropolitan Airport have been kept since the late 1940s.

"Just take it at face value and enjoy it," he said. "Don't look a gift horse in the mouth, because that heat is going to come around again."

Not this weekend, at least. A weak storm moving through Northern California could mean raindrops in the city, though any rain will likely be measured in mere hundredths of an inch, Powell said. As usual with these systems, areas farther north will probably get more rain.

Still, it'll be overcast and cool - a perfect prelude to fall, which starts at 1:44 p.m. Sunday.